检索结果-内蒙古大学图书馆

Workshops on Applications and the Internet (SAINT)

作者： K. Onuma T. Boku M. Sato D. Takahashi H. Susa M. Umemura Doctoral Program of Systems and Information Engineering University of Tsukuba Japan Institute of Information Sciences and Electronics Centre for Computational Physics University of Tsukuba Japan Department of Physics Rikkyo University Japan Institute of Physics Centre for Computational Physics University of Tsukuba Japan

We have developed a hybrid computing system named HMCS-G (Grid-enabled Heterogeneous Multi-Computer System) which combines multiple cluster systems and a special purpose machine for gravity calculations. The purpose of HMCS-G is to provide ideal computation environment for computational astrophysics, which requires multiple physics phenomena for precise and detailed simulation. There are two categories of machines required for this system, that is, multiple PC-clusters for general purpose computation such as hydro-dynamics and a special purpose machine GRAPE-6 which calculates gravity for all pairs of particles in the system with very high-speed. These systems are connected with a grid-RPC named OmniRPC which supports Globus and ssh for authentication. Our HMCS-G enables the worldwide access to GRAPE-6 cluster which provides several TFLOPS performance for gravity calculation. All participating PC-clusters share this resource in time sharing manner with grid technology. For efficient usage of GRAPE-6 resource, we modified the original server cluster of it for multiple clients running in various network environment. Currently, precise simulations on galaxy formation are being performed on clusters in several institutes with smoothed particle hydrodynamics and radiative transfer under complete gravity calculation, as the first real application on HMCS-G.

关键词： Astrophysics Gravity Pipelines physics computing Grid computing Computational modeling Authentication Time sharing computer systems File servers Network servers

来源：评论

学校读者我要写书评

暂无评论

Integrating Biomaterials into Microsystems: Formation and Characterization of Nanostructured Titania

引用

MRS Online Proceedings Library 2004年第1期820卷 218-223页

作者： Zuruzi Abu Samah Blaine C. Butler Emily R. Parker Ayesha Ahmed Heather M. Evans Cyrus R. Safinya Noel C. MacDonald Materials Department and Mechanical and Environmental Engineering Department University of California Santa Barbara U.S.A. Materials Department Physics Department and Biomolecular Science and Engineering Program University of California Santa Barbara U.S.A.

We demonstrate the facile fabrication of crack-free nanostructured crystalline titania into microsystems. Titania layers were formed by reacting Ti thin films, deposited by evaporation and sputtering, with aqueous H2O2. Cracks were observed in titania layers formed on blanket Ti films but absent on arrays of patterned Ti pads below a threshold dimension. Nanostructured titania formed from sputtered and evaporated Ti films consists of aligned fibrous and sponge-like nanoporous morphologies, respectively. Rat fibroblasts L-cells cultured on these titania fibers remain viable up to 3 days. These observations demonstrate the feasibility of this technique to integrate nanostructured titania into Nano|Micro-Electromechanical systems (N|MEMS) devices.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Evidence for a coupled magnetic-crystallographic transformation in Nd5(Si0.6Ge0.4)4

引用

Physical Review B 2004年第22期70卷 224429-224429页

作者： C. Magen L. Morellon P. A. Algarabel M. R. Ibarra C. Ritter A. O. Pecharsky K. A. Gschneidner, Jr. V. K. Pecharsky Materials and Engineering Physics Program Ames Laboratory Iowa State University Ames Iowa 50011-3020 USA and Department of Materials Science and Engineering Iowa State University Ames Iowa 50011-2300 USA

We have performed a detailed study of the magnetic and structural properties of the compound Nd5(Si0.6Ge0.4)4 by means of neutron powder diffraction, magnetization, linear thermal expansion, and magnetostriction experiments. A coupled magnetic and crystallographic first-order transformation from a room-temperature monoclinic Gd5Si2Ge2-type paramagnetic state to a low-temperature orthorhombic Gd5Si4-type ferromagnetic structure takes place on cooling at ∼68K. This magnetostructural transition shifts towards higher temperatures by the application of an external magnetic field at a rate of 0.11(1)K∕kOe, which is lower than the ∼0.6to∼0.3K∕kOe observed in the Gd5(SixGe1−x)4 and Tb5(SixGe1−x)4 compounds. The magnetostructural transformation cannot be completed in the isothermal regime by a 120kOe magnetic field. It is suggested that the single-ion anisotropy of the Nd ions hinders the completion of the field-induced transformation. The existence of a simultaneous magnetic and crystallographic transformation in this alloy, which is in sharp contrast with other previously studied Nd5(SixGe1−x)4 alloys, is discussed in terms of the role of interstitial impurities in triggering and coupling/decoupling the crystallographic transition.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A Monte Carlo CT model of the RANDO [registered trademark] Phantom

A Monte Carlo CT model of the RANDO [registered trademark] P...

引用

2004 Annual Meeting - American Nuclear Society

作者： Wang, Brian Xu, X. George Kim, Chan-Hyeong Nucl. Eng./Eng. Physics Program Rensselaer Polytechnic Institute Troy NY 12180 United States Nuclear Engineering Department Hanyang University 17 Haengdang-dong Sungdong-gu Seoul 133-791 Korea Republic of

No abstract available

关键词：

来源：评论

学校读者我要写书评

暂无评论

Passive decay heat removal in a fluidized bed nuclear reactor

Passive decay heat removal in a fluidized bed nuclear reacto...

引用

PHYSOR 2004: The physics of Fuel Cycles and Advanced Nuclear Systems - Global Developments

作者： Agung, A. Lathouwers, D. Van Der Hagen, T.H.J.J. Van Dam, H. Pain, C.C. De Oliveira, C.R.E. Goddard, A.J.H. Eaton, M.D. Gomes, J.L.M.A. Miles, B. Interfaculty Reactor Institute Delft University of Technology Mekelweg 15 2629 JB Delft Netherlands Department of Earth Science and Engineering Imperial College of Science Technology and Medicine London SW7 2BP United Kingdom Nuclear and Radiological Engineering and Medical Physics Program George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta GA 30332-0405 United States

ISBN: (纸本)0894486837

Numerical simulations have been performed to investigate the possibility of passive decay heat removal in a fluidized bed nuclear reactor. The conduction, convection and radiative heat transfer were included and the high Reynolds number k-Ε turbulence model was applied for the flow calculations. A P 1 approximation method for participating media was used for the radiation model. The reactor was modeled as a 2D axisymmetric cylinder. Calculations were performed for different initial total operating power to see whether the associated decay heat can be removed by passive means without compromising the safety margin. The results show the decay heat can be removed by passive means up to operating powers of about 55 MW. Further the results showed that all heat transfer mechanisms are of importance to remove heat from the bed of fuel particles to the reflector.

关键词： Nuclear reactors

来源：评论

学校读者我要写书评

暂无评论

Reversible spin-flop and irreversible metamagneticlike transitions induced by a magnetic field in the layered Gd5Ge4 antiferromagnet

引用

Physical Review B 2004年第14期69卷 144428-144428页

作者： E. M. Levin K. A. Gschneidner, Jr. T. A. Lograsso D. L. Schlagel V. K. Pecharsky Department of Physics and Astronomy Iowa State University Ames Iowa 50011-3160 USA Materials and Engineering Physics Program Ames Laboratory Iowa State University Ames Iowa 50011-3020 USA Department of Materials Science and Engineering Iowa State University Ames Iowa 50011-2300 USA

Temperature and magnetic field dependencies of the magnetization of single crystal Gd5Ge4 indicate antiferromagnetic coupling along the c direction below 130 K. Both a reversible spin-flop transition when a magnetic field of ∼8.4kOe is applied along the c direction, and irreversible metamagneticlike transitions when a 20 kOe or greater magnetic field is applied at 4.3 K along any of the three crystallographic axes are observed. Although Gd3+ ions have negligible single ion anisotropy, the metamagnetic transitions and magnetization of Gd5Ge4 in the ferromagnetic state depend on the crystallographic direction reflecting the anisotropy of the exchange interactions due to the distinctly layered Sm5Ge4-type crystal structure.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Phase relationships and structural, magnetic, and thermodynamic properties of alloys in the pseudobinary Er5Si4−Er5Ge4 system

引用

Physical Review B 2004年第14期70卷 144419-144419页

作者： A. O. Pecharsky K. A. Gschneidner, Jr. V. K. Pecharsky D. L. Schlagel T. A. Lograsso Materials and Engineering Physics Program Ames Laboratory of the United States Department of Energy Iowa State University Ames Iowa 50011-3020 USA Department of Materials Science and Engineering Iowa State University Ames Iowa 50011-2300 USA

The room temperature crystal structures of Er5SixGe4−x alloys change systematically with the concentration of Ge from the orthorhombic Gd5Si4-type when x=4, to the monoclinic Gd5Si2Ge2 type when 3.5⩽x⩽3.9 and to the orthorhombic Sm5Ge4 type for x⩽3. The Curie-Weiss behavior of Er5SixGe4−x materials is consistent with the Er3+ state. The compounds order magnetically below 30K, apparently adopting complex noncollinear magnetic structures with magnetization not reaching saturation in 50kOe magnetic fields. In Er5Si4, the structural-only transformation from the monoclinic Gd5Si2Ge2-type to the orthorhombic Gd5Si4-type phase occurs around 218K on heating. Intriguingly, the temperature of this polymorphic transformation is weakly dependent on magnetic fields as low as 40kOe (dT∕dH=−0.058K∕kOe) when the material is in the paramagnetic state nearly 200K above its spontaneous magnetic ordering temperature. It appears that a magnetostructural transition may be induced in the 5:4 erbium silicide at ∼18K and above by 75kOe and higher magnetic fields. Only Er5Si4 but none of the other studied Er5SixGe4−x alloys exhibit magnetic field induced transformations, which are quite common in the closely related Gd5SixGe4−x system. The magnetocaloric effects of the Er5SixGe4−x alloys are moderate.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A nanoscale approach to stamp fabrication in hard materials using high intensity ultrafast lasers

A nanoscale approach to stamp fabrication in hard materials ...

引用

2003 MRS Fall Meeting

作者： McDonald, Joel P. Picard, Yoosuf N. Yalisove, Steven M. Liu, Hsiao-Hua Blaszczak, Joseph Guo, Lingji J. Dept. of Materials Science and Engineering University of Michigan Ann Arbor MI 48109-2176 United States Center for Ultrafast Optical Science University of Michigan Ann Arbor MI 48109-2099 United States Applied Physics Program University of Michigan Ann Arbor MI 48109-1120 United States Dept. of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122

Nanomorphing with ultrafast lasers may have a significant role in direct write stamp production. Surface conditions play a critical role in the ablative properties of materials. We have conducted femtosecond laser (pulse duration;120 fs, wavelength;780 nm) threshold studies of silicon with the native oxide and silicon with atomically clean surfaces in an ultra-high vacuum environment. We have discovered that a -1.5 nm thick oxide layer can alter the ablation threshold of Si (100) by 25 ± 5%. Additionally, our work has shown that collateral damage can be controlled on the nanoscale. Transmission electron microscopy (TEM) images of femtosecond laser machined holes in Si (100) show that collateral damage extends only 10 nm from the edge. © 2004 Materials Research Society.

关键词： Ultrafast phenomena

来源：评论

学校读者我要写书评

暂无评论

Micro-bathymetric mapping using acoustic range images

Micro-bathymetric mapping using acoustic range images

引用

OCEANS

作者： C. Roman H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This work focuses on the creation of high resolution micro-bathymetric maps using a high frequency pencil beam sonar. These maps typically cover areas of 10's to 100's of square meters. Data is collected using a sonar mounted to an underwater vehicle that can be positioned at discrete locations on the sea floor or flown in a survey pattern above the bottom. Specifically, we are focused on improving the accuracy of these terrain maps by merging sonar pings taken from multiple vantage points over the same location. This requires the adaption of data registration techniques to handle errors related to the sonar sensor. The registration can also be modified to incorporate the navigation data available from an instrumented underwater vehicle. A two axis scanning sonar was used to gather data in the form of densely sampled range images. The data registration works on the 3D projection of these range images in a scan-matching manner. Through this process regions occluded in a single scan are filled with data available from other scans and individual pings which show a poor return are removed. Refined estimates of the scan vantage points are also generated during the registration. The initial estimates of these locations are provided by navigation data. The practical application of this work complements photographic mapping when visibility is limited. It also provides additional measurements which can be used to improve vehicle navigation.

关键词： Sonar navigation Sonar measurements Remotely operated vehicles Underwater vehicles Sea floor Underwater acoustics Layout Oceans Acoustical engineering Acoustic beams

来源：评论

学校读者我要写书评

暂无评论

Visually augmented navigation in an unstructured environment using a delayed state history

Visually augmented navigation in an unstructured environment...

引用

IEEE International Conference on Robotics and Automation (ICRA)

作者： R. Eustice O. Pizarro H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This work describes a framework for sensor fusion of navigation data with camera-based 5 DOF relative pose measurements for 6 DOF vehicle motion in an unstructured 3D underwater environment. The fundamental goal of this work is to concurrently estimate online current vehicle position and its past trajectory. This goal is framed within the context of improving mobile robot navigation to support sub-sea science and exploration. Vehicle trajectory is represented by a history of poses in an augmented state Kalman filter. Camera spatial constraints from overlapping imagery provide partial observation of these poses and are used to enforce consistency and provide a mechanism for loop-closure. The multi-sensor camera + navigation framework is shown to have compelling advantages over a camera-only based approach by: 1) improving the robustness of pairwise image registration, 2) setting the free gauge scale, and 3) allowing for a unconnected camera graph topology. Results are shown for a real world data set collected by an autonomous underwater vehicle in an unstructured undersea environment.

关键词： Navigation Delay History Cameras Underwater vehicles Robot vision systems Sensor fusion Motion measurement Mobile robots Robustness

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：